From the Stars Without Number Compatible – Alien Database
Rust Metal. Rustphagus has a couple of antennas that secrete an oxidizing substance capable of affecting iron-like metals (iron, titanium, nickel, and the like). The antennas have a reach of 3 meters and they automatically hit any target unless a successful Evasion/Dexterity saving throw is made.
COMBAT & TACTICS
Rustphagus is not aggressive and easy to tame. They do not attack other life forms, and even if threatened they prefer to run or hide. The only harm they can cause is to accidentally eat some metallic components, however, if let unguarded they may easily provoke immense damage to buildings.
DESCRIPTION
These docile and insect-like creatures can grow to the size of a cow. Depending on the strain, they may have from two to four pairs of legs, and their color varies from dark brown to dark yellow or sometimes rust red.
HABITAT
Rustphagus are grazers by nature, you can encounter a herd of these creatures wandering on rocky badlands cleaning the soil from small plants rich in metals and surface deposits of ferrous ore. They also thrive in subterranean caves and abandoned mines, where they can find plenty of ferrous ore or abandoned equipment. Primitive cultures make great use of these creatures as pulling animals and for locating hidden deposits of iron.
BIOLOGY
The biology of a Rustphagus relies on ferrous metals to activate its metabolism. It is considered a very peculiar being by most xenobiologists, which has found many uses for the enzyme secreted by their antennas. Their metabolism is extremely efficient and can endure without food for days if necessary.